1. Field of the Invention
The present invention relates to a method for data processing, and more particularly, to a method for data compressing/decompressing.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a raw over-drive table without compression. Generally, for enhancing response time of liquid crystal particles in a Liquid Crystal Display (LCD), manner of over-driving is used when liquid crystal particles are driven. The liquid crystal particles of one pixel of the LCD can be driven with a corresponding over-drive grey level according to the original grey levels of the pixel in a current frame and the frame previous to the current frame. An appropriate over-drive grey level can be looked up in the over-drive table as illustrated in FIG. 1 and be used to drive the pixel for enhancing the response time of the pixel. As shown in FIG. 1, F1 (column) represents the original grey level of one pixel in one frame (the previous frame), and F2 (row) represents the original grey level of the pixel in the frame next to the frame (the current frame). Under the condition that one color is divided into 256 grey levels (8 bits), the over-drive table sizes up to 256×256×256 bits (equals to 32 Kbytes). However, a normal driving chip for LCD cannot afford that big size to store all the data of the over-drive grey levels.
Please refer to FIG. 2. FIG. 2 is a diagram illustrating an over-drive table after reduction. As shown in FIG. 2, the data in the table of FIG. 2 is reduced by decreasing the resolution of the table of FIG. 1 and abandoning some data in the table of FIG. 1. For example, if the original grey level of one pixel in the previous frame falls in the range between the grey levels “0”˜“32”, and the original grey level of that pixel in the current frame falls in the range between the grey levels “32”˜“64”, the corresponding over-drive grey level is grey level “0”. In this way, the over-drive table of FIG. 2 can be reduced to 8×8×256 bits (64 bytes), which is obviously much smaller than the raw over-drive table of FIG. 1. However, the reduction from the table of FIG. 1 to the table of FIG. 2 results in insufficiently over-driving, decreasing the response time of the liquid crystal particles, and distortion in the displayed frames.
Please refer to FIG. 3. FIG. 3 is a diagram illustrating a conventional over-drive device 10. As shown in FIG. 3, the over-drive device 10 comprises a determining device 41, an over-drive table 42, and a memory device 43. The over-drive table 42 stores a plurality of over-drive grey levels. Each over-drive grey level represents a corresponding voltage according to a gamma curve disposed for the LCD. Therefore, a pixel can be over-driven by the voltage corresponding to one over-drive grey level according to the gamma curve. Assuming a plurality of frames are displayed on the LCD, hereinafter only two adjacent frames “f”, and “f−1” of the plurality of the frames are illustrated for the operation of the over-drive device 10, where the frame “f−1” represents a frame previous to the frame “f”, P(f−1,n) represents an original grey level of a pixel “n” in the frame “f−1”, and P(f,n) represents an original grey level of a pixel “n” in the frame “f”. The memory device 43 stores original grey levels of all pixels in one frame “f−1”. When the LCD completes displaying the frame “f−1” and is going to display frame “f”, the determining device 41 chooses an over-drive grey level from the over-drive table 42 according to the original grey levels P(f,n) and P(f−1, n) for over-driving the pixel “n” in the frame “f”. For example, when the original grey level P(f,n) is “32” (as the rows shown in FIG. 2), and the original grey level P(f−1,n) is “128” (as the columns shown in FIG. 2), the corresponding over-drive grey level is “24”.